Current commercial decaffeination of coffee is effected by the removal of caffeine from whole, green coffee beans. The beans are first moistened and then extracted with a solvent which is relatively specific for caffeine. The solvents employed commercially are either a halogenated hydrocarbon solvent, such as discussed in U.S. Pat. No. 3,671,263 to Patel et al. or a caffeine-deficient water solution of coffee solubles, such as disclosed in U.S. Pat. No. 2,309,092 to Berry et al., both of which are herein incorporated by reference.
In the decaffeination process of U.S. Pat. No. 2,309,092 which is commonly referred to as the water extraction system (Note: Sivetz, Coffee Processing Technology, Vol. 2, p. 208, AVI Publishing Co., Inc., 1963) the caffeine laden water extract, resulting from contact between caffeine-containing green coffee and the caffeine-deficient water solution, is solvent extracted with one of the same hydrocarbon caffeine solvents which are employed in the direct solvent extraction processes exemplified by the aforementioned 3,671,263 patent.
As a result of the presence of halogenated hydrocarbon solvents, in commerical green bean decaffeination processes, the decaffeinated coffee products presently being sold, either roasted and ground or soluble, contain at least trace amounts of halogenated compounds. This solvent residue can impart an off-flavor to coffee beverages and its presence within coffee products is becoming the subject of increasingly stringent governmental regulation.
Thus, the coffee industry is desirous of finding alternative systems for decaffeination which will avoid the use of halogenated solvents. Alcohols such as ethanol, have long been known as solvents for caffeine; however, their use in extracting caffeine from green coffee, which must of necessity be moistened with water, or from an aqueous extract of green coffee has not been considered practical because of their miscibility with water. The use of caffeine solvents which have boiling points above that of water, such as triacetin (B.P. 276.degree. C.) and diethyl ketone (B.P. 102.degree. C.) have also not previously been considered practical for commerical use.